01:119:116 Lecture Notes - Lecture 6: Gastrovascular Cavity, Gastrointestinal Tract, Symmetry In Biology
15 Mar 2016
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Typical: sac-like body, osculum open end, spongocoel. Phylum platyhelminthes: dorsoventrally flattened, triploblastic, bilateral symmetry, acoelomate, free-living. Phylum rotifera fig 33. 13: marine, freshwater, damp soil, 50 microm 2mm, multicellular. 2 openings: crown of cilia of head. Draws vertex of water in mouth: trophi. Shell - 2 part, hinged, secreted by mantle. Body wall, coelam and many internal organs divided into segments. Digestive tract not segmented: marine, freshwater, damp soil, ex. Phylum newatoda: roundworms, soil, aquatic, parasitic, cuticle, pseudocoelamates. Phylum arthropoda: most species, coelamate, structure. Phylum echinodermata: larva bilateral system, adult - five part symmetry, endoskeleton. Spines project out through epidermis: water vascular system. Phylum chordata: includes invertebrates and vertebrates (cid:1) Forerunner of backbone: dorsal, hollow nerve cord. Develops into central nervous system: pharyngeal gill slits. Replaces notochord: possess 2 or more sets of hox genes. Gnathostomes: jaws, four sets of hox genes. Support weight on land: neck, fused pelvic girdle. Allows amniotes to complete life cycle on land: rib cage ventilation.
